JP3089687B2 - Fuel evaporative gas state detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in an apparatus for preventing the evaporation of fuel evaporative gas generated in a fuel supply system of a vehicle, and detects the amount of fuel evaporative gas generated in a fuel tank. The present invention relates to a gas state detection device.

[0002]

2. Description of the Related Art In general, there is known a fuel evaporation prevention device for preventing a fuel evaporative gas generated in a fuel tank from being released into the atmosphere. This involves adsorbing the fuel evaporative gas generated in the fuel tank to an adsorbent disposed in the canister, and then, using the negative pressure in the intake pipe, sucks the adsorbed fuel evaporative gas together with fresh air sucked from the air opening hole of the canister. It is introduced into the intake pipe according to the operation state.

In such a device, a pressure sensor for detecting the pressure in the fuel tank is provided for the purpose of detecting the amount of fuel evaporative gas generated in the fuel tank (see, for example, Japanese Patent Application Laid-Open No. 2-102). No. 136558). This means that only the pressure in the fuel tank is detected by the pressure sensor, and it is determined that the greater the pressure in the fuel tank, the more fuel evaporative gas is generated.

[0004]

However, the inside of the fuel tank is not completely closed to the atmosphere, and the fuel tank is always open to the atmosphere through the air opening hole of the canister, or the fuel tank is temporarily closed. It opens to the atmosphere through a control valve arranged in the air conditioner.

For this reason, the pressure in the fuel tank is greatly affected by the atmospheric pressure, that is, the pressure in the fuel tank varies depending on the atmospheric pressure at that time regardless of the generation of the fuel evaporative gas.

[0006] Therefore, the above-mentioned method (a method of simply detecting only the pressure in the fuel tank using a pressure sensor and obtaining the amount of generated fuel evaporative gas based on the pressure in the fuel tank) is as described above. When the pressure in the fuel tank rises due to the influence of atmospheric pressure, it is erroneously detected that a large amount of fuel evaporative gas is generated even though only a small amount of fuel evaporative gas is generated. There was fear.

On the contrary, when the pressure drops in the fuel tank due to the influence of the atmospheric pressure, only a small amount of the fuel evaporative gas is generated despite the large amount of the fuel evaporative gas being generated. Otherwise, there is a risk of erroneous detection.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to accurately detect the amount of fuel gas generated in a fuel tank irrespective of fluctuations in fuel tank pressure due to atmospheric pressure. It is an object of the present invention to provide a fuel-evaporated-gas state detecting device which can be used.

[0009]

In order to achieve the above object, a fuel evaporative gas state detecting device according to the present invention has an atmospheric pressure detecting means for detecting an atmospheric pressure and a fuel for containing a liquid fuel as shown in FIG. A tank pressure detecting means for detecting a pressure in the tank, and a fuel for detecting an amount of fuel evaporative gas generated in the fuel tank based on a detection result of the atmospheric pressure detecting means and the tank pressure detecting means. A technical means including an evaporative gas generation amount detecting means is employed.

[0010] Further, a pressure detecting means for detecting a pressure, a first connecting part opened to the atmosphere, a second connecting part connected to the fuel tank, and a third connecting part connected to the pressure detecting means.
A three-way switching valve that has three connecting portions with a connecting portion and communicates one of the pressure detecting means or the fuel tank and the pressure detecting means with the atmosphere and the three-way switching valve; A control signal output device for outputting a control signal for controlling the three-way switching valve to communicate the pressure detection means with the atmosphere, and an atmospheric pressure detected by the pressure detection means at this time; A fuel evaporation device that controls a three-way switching valve to communicate the pressure detection means with the fuel tank, and detects the amount of fuel evaporative gas generated based on the pressure in the fuel tank detected by the pressure detection means at this time. Technical means of providing a gas generation amount detecting means may be employed.

[0011]

According to the present invention, the amount of fuel evaporative gas generated in the fuel tank is detected based on the detection result of the atmospheric pressure detecting means and the tank pressure detecting means for detecting the pressure in the fuel tank. .

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment shown in the drawings. FIG. 2 is an overall configuration diagram showing a configuration of a fuel evaporation prevention apparatus according to an embodiment using the fuel evaporation gas state detection apparatus of the present invention and an abnormality detection apparatus for the fuel evaporation prevention apparatus for detecting an abnormality of the fuel evaporation prevention apparatus. It is.

The intake air sucked through the air cleaner 1 for purifying the air passes through an intake pipe 2 provided continuously to the air cleaner 1 and is surrounded by an internal combustion engine body 14 and a piston 12. It is supplied to the combustion chamber 16. A throttle valve 8 that opens and closes in conjunction with an accelerator pedal 6 and controls the amount of intake air is disposed in the intake pipe 2. An intake valve 10 that opens and closes by the rotational force of a camshaft that is not provided is provided.

The combustion chamber 16 is connected to an exhaust pipe 20, and combustion gas generated in the combustion chamber 16 during the explosion stroke of the internal combustion engine is discharged from the combustion chamber 16 through the exhaust pipe 20. At the boundary between the combustion chamber 16 and the exhaust pipe 20, similarly to the intake valve 10, an exhaust valve 18 that opens and closes by the rotational force of a camshaft (not shown) is provided. An oxygen sensor 21 for detecting the concentration is provided.

On the other hand, the liquid fuel stored in the fuel tank 22 is pumped up by a fuel pump 24 and sent to an injector 26 provided in the intake pipe 2 under pressure. Then, the injector 26 supplies the fuel to the combustion chamber 16 at an optimum fuel injection amount and injection timing based on a calculation result of the electronic control device 50 described later.

The fuel tank 22 includes a fuel tank 22.
An absolute pressure sensor 25, which constitutes a main part of the present invention for detecting the internal pressure and serves as an atmospheric pressure detecting means and a tank pressure detecting means, is provided via a three-way switching valve 23. The three-way switching valve 23 switches the fuel tank 22 or a passage connecting the atmospheric pressure to the absolute pressure sensor 25 based on an output signal from an electronic control unit 50 described later.
Further, a communication pipe 28 is connected to the fuel tank 22, and a check valve 29 is provided on a part of the communication pipe 28. The check valve 29 is configured so that the pressure in the fuel tank 22 is a predetermined value P ₀ (P ₀ = atmospheric pressure + α, α is, for example, 15 mmH).
g) or more, the valve is opened, and the fuel vapor generated in the fuel tank is introduced into the canister 30.

An adsorbent 34 containing activated carbon therein is provided in the canister 30. The adsorbent 34 adsorbs harmful components (fuel vapor) in the fuel vapor gas.

On the other hand, one end of the canister 30 is provided with an atmosphere opening hole 36 opened to the atmosphere, and the other end of the canister 30 is connected to the hose connection portion 3 through an adsorbent 34.
The supply pipe 38 is connected to the hose connection part 31.

The other end of the supply pipe 38 is connected to one end of a control valve 40, and the other end of the control valve 40 is connected to a supply pipe 42 connected to the intake pipe 2. The pipe 2 is connected via a control valve 40.

The supply pipe 38 and the supply pipe 42 are made of a flexible material such as a rubber hose or a nylon hose. Further, the control valve 40 performs an opening / closing operation based on a control signal from an electronic control device 50 described later, and connects or disconnects the canister 30 and the intake pipe 2.

Electronic control unit (hereinafter referred to as ECU) 50
Sets appropriate control amounts of the fuel system and the ignition system based on detection signals from respective sensors (not shown),
6, a known control device that outputs a control signal for appropriately controlling the control valve 40, an ignition device (not shown), and the like.

The ECU 50 includes a known CPU 52 for performing arithmetic processing, a read-only ROM 54 for storing a control program and control constants necessary for the arithmetic operation, and a RAM 56 for temporarily storing arithmetic data during the operation of the CPU 52. , And an input / output circuit 58 for inputting / outputting a signal from outside the ECU 50.

The ECU 50 drives the three-way switching valve 23 to output a control signal for communicating either the absolute pressure sensor 25 with the fuel tank 22 or the absolute pressure sensor 25 with the atmospheric pressure. Means and a fuel evaporative gas generation amount detecting means for detecting the amount of fuel evaporative gas generated in the fuel tank 22 based on the atmospheric pressure and the pressure in the fuel tank 22 are provided.

Next, the operation of the fuel evaporation prevention device for preventing the fuel evaporation gas from evaporating into the atmosphere will be described. Fuel evaporative gas is generated in the fuel tank 22 and the fuel tank 2
When the pressure in the fuel tank 2 becomes equal to or higher than a predetermined value P ₀ , the check valve 29 is opened, and the fuel evaporative gas is introduced into the canister 30 through the check valve 29 and the communication pipe 28, and the harmful gas in the fuel evaporative gas is removed. The components are adsorbed on the adsorbent 34 in the canister 30.

Thereafter, when the ECU 50 determines that the internal combustion engine is in a state where fuel evaporative gas can be introduced into the intake pipe 2 by a method described later, the control valve 40 is opened. When the control valve 40 is in the open state, fresh air is sucked into the canister 30 through the atmosphere opening hole 36 by the negative pressure in the intake pipe 2. As the fresh air is sucked into the canister 30, harmful components in the fuel evaporative gas adsorbed by the adsorbent 34 are introduced into the intake pipe 2 together with the fresh air. Repeated use is possible. Then, the fuel evaporative gas introduced into the intake pipe 2 together with the fuel injected from the injector 26
Used for combustion in the combustion chamber 16.

When the ECU 50 determines that the internal combustion engine is in a state in which fuel evaporative gas must not be introduced into the intake pipe 2, the control valve 40 is closed, and harmful components in the fuel evaporative gas are removed from the canister 30 again. Is adsorbed by the adsorbent 34.

Next, the operation of the fuel evaporative gas state detecting device according to the present invention will be described with reference to the flowchart shown in FIG. This routine is executed every predetermined time (for example, every 60 ms) when a key switch (not shown) is turned on.

[0028] controls the step 100, the three-way valve 23 outputs a control signal for communicating the absolute pressure sensor 25 air reads the atmospheric pressure P _a, which is detected by the absolute pressure sensor 25 in step 110, It is stored in the ROM 54.

In step 120, this time the fuel tank 22
A control signal for causing the absolute pressure sensor 25 to communicate with the
Rectangular output to switching valve 23, the pressure in the fuel tank detected by the absolute pressure sensor 25 in step 130 (hereinafter, referred to as tank pressure) reads P _f.

[0030] by subtracting the atmospheric pressure P _a stored from step 140 in tank pressure P _f in ROM 54, calculates the deviation P _fa the tank pressure P _f and the atmospheric pressure P _a. That is, the pressure fluctuation in the fuel tank 22 due to the generation of the fuel evaporative gas is detected.

[0031] Based on the P _fa value obtained in step 150 In step 140, determine the fuel evaporation gas generation amount EVP map as shown in FIG. 9, and then returns stored in RAM 56.

Accordingly, the tank pressure _Pf and the atmospheric pressure P
_Since the fuel evaporative gas generation amount EVP is obtained based on the deviation P _fa from the fuel tank 2, the fuel tank 2
2. Evaporated gas generation amount EVP always regardless of the pressure fluctuation of 2.
Can be determined accurately.

FIG. 4 is a flow chart showing the operation when controlling each control factor of the fuel evaporation prevention device based on the fuel evaporative gas generation amount EVP set by the above-described method. Note that the routine of FIG. 4 is executed every predetermined time (for example, every 60 ms), similarly to the routine of FIG.

At step 180, step 150 of FIG.
Is read, and the fuel evaporation gas generation amount EVP stored in the RAM 56 is read. In step 190, the ECU 5
The timer (not shown) within 0 is checked, and if the time by the timer is 0 to 4 seconds, the process proceeds to step 200 to execute an abnormality determination routine described later, and the time by the timer is 4 to 4 seconds.
If it is 30 seconds, the routine proceeds to step 300, where a process for setting a duty ratio for controlling the opening and closing of the control valve 40 based on the fuel vapor generation amount EVP is executed.

FIG. 5 shows the details of each process of the abnormality determination routine. In step 201, the fuel vapor generation amount EVP calculated in step 150 and the predetermined value K
It is determined whether the fuel vapor 22 is sufficiently generated in the fuel tank 22 by comparing the EVP with the EVP. Here, if the fuel vapor generation amount EVP is equal to or more than the predetermined value KEVP, it is determined that the fuel gas is sufficiently generated in the fuel tank 22 and the process proceeds to step 202. If the fuel evaporation gas generation amount EVP is equal to or higher than the predetermined value KEVP, If not, it is determined that the fuel gas is not sufficiently generated in the fuel tank 22, and the routine ends.

The predetermined value KEVP is a fuel evaporative gas generation amount EVP which can change the air-fuel ratio of the internal combustion engine, which will be described later, by introducing the fuel evaporative gas into the intake pipe 2. This value is an experimental value. Is a value that is typically set. Further, the value of the predetermined value KEVP is a value sufficiently larger than the amount of generated fuel evaporative gas when achieving the pressure P ₀ in the fuel tank 22 at which the check valve 29 can be opened.

In step 202, the control valve 40 is fully closed to prohibit the introduction of the fuel evaporative gas into the intake pipe 2. In step 203, it is determined whether or not the determination condition is satisfied. If the determination condition is satisfied, step 2 is executed.
The routine proceeds to 04, and if the determination condition is not satisfied, this routine ends. Here, the determination condition is, for example, that the feedback correction coefficient FAF at that time is within a predetermined range (for example, 0.
7 <FAF <1.2), it is determined that the determination condition is satisfied.

In step 204, it is determined whether or not the oxygen sensor 21 is operating normally. If the oxygen sensor 21 is not operating normally, this routine ends. This is because the voltage value of the output signal of the oxygen sensor 21 is equal to the boundary voltages V1 and V1 as shown in FIG.
To make sure that it is changing across 2
If it changes crossing, it is determined that the oxygen sensor 21 is operating normally.

In step 205, the control valve 40 is opened, and an average value IFAF1 of n times (for example, n = 6) of the feedback correction coefficient FAF after the valve is opened is advanced to step 206. In step 206, the control valve is opened. 40 and the feedback correction coefficient FAF after the valve is closed.
An average value IFAF2 for n times is calculated.

In step 207, the average value IFAF1
And the average value IFAF2, that is, the average value IFA
If the deviation between F2 and the average value IFAF1 is equal to or greater than the predetermined value β, when the control valve 40 changes from the open state to the closed state, it is determined that the air-fuel ratio has become lean. In general, if the fuel evaporation prevention device is operating normally, the air-fuel ratio becomes lean when the control valve 40 changes from the open state to the closed state as shown in FIG. , 42 are disengaged or closed, the fuel evaporative gas is emitted even if the control valve 40 changes from the open state to the closed state as shown in FIG. Is not introduced into the intake pipe 2, the air-fuel ratio does not change.

Therefore, the air-fuel ratio does not change in step 207, that is, the average value IFAF2 and the average value IF
If the deviation from AF1 is not greater than or equal to the predetermined value β, it is determined that an abnormality has occurred in the fuel evaporation prevention apparatus, and the routine proceeds to step 208, where abnormality is set in step 208, and this routine ends.

The abnormal setting is to store, for example, information that an abnormality has occurred in the ROM 56. Then, for example, in another routine (not shown), the information in the ROM 56 is read and accumulated and calculated a predetermined number of times (for example, three times). If it is determined that the abnormality has been set continuously for the above times, a known fail-safe operation such as turning on the display lamp 60 to notify the vehicle user or the like that the abnormality has occurred is executed.

On the other hand, in step 207, the air-fuel ratio becomes lean, that is, the average value IFAF2 and the average value IFA
If the deviation from F1 is equal to or greater than the predetermined value β, it is determined that the fuel evaporation prevention device is operating normally, and the process proceeds to step 209. In step 209, the normal setting is executed, and this routine ends. Here, the normal setting is to store, for example, information that the fuel evaporation prevention device is operating normally in the ROM 56, and by reading this information in another routine, the value that has been cumulatively calculated so far is read. It is to reset.

Accordingly, by performing such an operation, it is possible to determine whether or not an abnormality has occurred in the fuel evaporation prevention device. At this time, the present invention accurately detects whether or not sufficient fuel evaporative gas has been generated to change the air-fuel ratio of the internal combustion engine. In addition, since only a small amount of the fuel evaporative gas is generated, the erroneous determination that the air-fuel ratio does not change and the result is determined to be abnormal can be prevented.

FIG. 8 is a flowchart showing in detail a process for setting a duty ratio for controlling the opening and closing of the control valve 40 based on the fuel evaporative gas EVP obtained in the routine of FIG.

In step 301, it is determined whether or not the internal combustion engine is in the state of executing the duty ratio control of the control valve 40 in accordance with the amount of generated fuel vapor EVP, and the internal combustion engine is in the state of executing the duty ratio control. Then step 302
If it is not the internal combustion engine state in which the duty ratio control is to be executed, the process proceeds to step 306. In step 306, the duty ratio D ₀ is set to 0%, and the process proceeds to step 308.

The method of determining whether or not the internal combustion engine is in the state of executing the duty ratio control of the control valve 40 is, for example, performed for a predetermined time (for example, when the ignition switch is turned on).
120S) has elapsed and the cooling water temperature has reached a predetermined temperature (for example,
It is determined that the engine is in an internal combustion engine state in which the duty ratio control is executed when conditions such as not more than 40 ° C. and the fuel supply is not interrupted.

In step 302, the throttle valve 8 is checked, and the throttle opening θ is set to a predetermined angle (for example, 10 degrees).
°), it is determined whether or not the change amount Δθ of the throttle opening θ is equal to or less than a predetermined change amount (for example, 0.5 °). If not, step 30
Then, in step 307, the duty ratio D _{0 is set} to 2
The value is set to 0% and the process proceeds to step 308.

In step 303, the amount of generated fuel evaporative gas E
From VP, sets the basic duty ratio D _B of the control valve 40 by using the map shown in FIG. 10. Here, the more the fuel vapor generation amount EVP as shown in the map of FIG. 10, it is to set small the basic duty ratio D _B.

[0050] Based on the step 304 the throttle opening theta, obtains the correction coefficient K from the map shown in FIG. 11, setting the duty ratio D ₀ by multiplying the correction coefficient K to the basic duty ratio D _B In step 305 I do.

The output duty ratio D ₀ is set by executing the processing described above in step 308, the routine ends. As described above, the amount of generated fuel vapor EVP generated in the fuel tank 22 is accurately detected,
By reducing the duty ratio D ₀ when a large amount of fuel evaporative gas is generated, a large amount of fuel evaporative gas is introduced into the intake pipe 2 to prevent the combustion state of the internal combustion engine from fluctuating excessively. be able to.

Further, in this embodiment, the three-way switching valve 23
The provided, the deviation P between tank pressure P _f and the atmospheric pressure P _a, which is detected by the same pressure detecting means (absolute pressure sensor 25)
_Since the fuel evaporative gas generation amount EVP is obtained based on the _fa , an excellent effect that the fuel evaporative gas generation amount EVP can always be accurately obtained regardless of the temperature characteristics or the change with time of the absolute pressure sensor 25 itself. Get.

In this embodiment, the amount EVP of the fuel evaporative gas generated in the fuel tank 22 is accurately detected, and based on the amount EVP of the fuel evaporative gas, the abnormality detection operation and control of the fuel evaporation prevention device are performed. Duty ratio D _{0 of} valve 40
However, the present invention is not limited to this, and other control factors may be controlled using the amount of generated fuel vapor EVP.

[0054] Further, although detected a tank pressure P _f and the atmospheric pressure P _a with the same pressure detecting means (absolute pressure sensor 25) in the present embodiment to obtain the effect described above is not limited thereto , it may be provided with pressure detecting means for detecting a pressure detecting means and the tank pressure P _f for detecting the atmospheric pressure P _a separately.

In this embodiment, the absolute pressure sensor 25 is used as the pressure detecting means, but a relative pressure sensor may be used.

[0056]

As described above, in the present invention, the fuel evaporative gas generated in the fuel tank based on the detection result of the atmospheric pressure detecting means and the tank pressure detecting means for detecting the pressure in the fuel tank. By detecting the amount of fuel vapor generated, the excellent effect of being able to accurately detect the amount of fuel evaporative gas generated in the fuel tank regardless of fluctuations in the fuel tank pressure caused by the influence of atmospheric pressure. Play.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims of the present invention.

FIG. 2 is an overall configuration diagram showing a configuration of an apparatus according to an embodiment of the present invention.

FIG. 3 is a flowchart illustrating an operation of detecting an amount of generated fuel evaporative gas according to the present invention.

FIG. 4 is a flowchart for explaining an operation when controlling the apparatus shown in FIG. 2 based on the amount of generated fuel evaporative gas.

FIG. 5 is a flowchart showing details of the operation of the flowchart shown in FIG. 4;

FIG. 6 is a diagram for explaining the operation of the flowchart shown in FIG. 5;

FIG. 7 is a diagram which is used for describing the operation of the flowchart shown in FIG.

FIG. 8 is a flowchart for explaining the operation when controlling the apparatus shown in FIG. 2 based on the amount of generated fuel evaporative gas.

FIG. 9 is a diagram which is used for describing the operation of the flowchart shown in FIG.

FIG. 10 is a diagram which is used for describing the operation of the flowchart shown in FIG.

FIG. 11 is a diagram which is used for describing the operation of the flowchart shown in FIG.

[Explanation of symbols]

 2 Intake pipe 22 Fuel tank 23 Three-way switching valve 25 Absolute pressure sensor 29 Check valve 40 Control valve 50 Electronic control unit (ECU) 60 Indicator lamp

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02M 25/08 F02B 77/08

Claims (4)

(57) [Claims] 1. Atmospheric pressure detecting means for detecting atmospheric pressure; tank pressure detecting means for detecting pressure in a fuel tank containing a liquid fuel; detection result of the atmospheric pressure detecting means; detection hand stage of the detection result and the fuel evaporative emission state detecting device, characterized in that it comprises a fuel evaporation gas generation amount detecting means for detecting a fuel evaporation gas generation amount generated within the fuel tank based on. (2) Detection of the fuel evaporative gas generation amount detection means
An abnormality that detects an abnormality in the fuel evaporation prevention device based on the result
The fuel system according to claim 1, further comprising a detection unit.
Abnormality detection device for transpiration prevention device. (3) The abnormality detecting means includes a fuel evaporative gas
The amount of fuel evaporative gas generation detected by the generation amount detection means
Communicates / blocks the canister and intake pipe when it exceeds a certain amount
The control valve to open and close, and set the parameters related to the air-fuel ratio at this time.
Detecting abnormalities based on changes in data
The abnormality detection device for a fuel evaporation prevention device according to claim 2. (4) Pressure detection means for detecting pressure, Connected to the first connection opening to the atmosphere and the fuel tank.
The second connection part and the third connection part connected to the pressure detecting means.
It has three connections with the continuation part, and is connected to the atmosphere and the pressure detecting means.
Stage or any of the fuel tank and the pressure detecting means
A three-way switching valve for communicating one side, Control signal for switching control of the three-way switching valve
A control signal output device for outputting The three-way switching valve is controlled to control the pressure detecting means and the atmosphere.
To the inside, and at this time, the pressure detecting means
Controlling the detected atmospheric pressure and the three-way switching valve
The pressure detecting means and the fuel tank are communicated, and at this time,
Pressure in the fuel tank detected by the pressure detecting means
Fuel evaporation that detects the amount of fuel evaporative gas generated based on
And a gas generation amount detecting means.
Gas generation state detection device.